From owner-freebsd-hackers@FreeBSD.ORG Wed Sep 20 13:23:58 2006 Return-Path: X-Original-To: freebsd-hackers@freebsd.org Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id CDD2116A636 for ; Wed, 20 Sep 2006 13:23:58 +0000 (UTC) (envelope-from anderson@centtech.com) Received: from mh1.centtech.com (moat3.centtech.com [207.200.51.50]) by mx1.FreeBSD.org (Postfix) with ESMTP id 7D13543D76 for ; Wed, 20 Sep 2006 13:23:57 +0000 (GMT) (envelope-from anderson@centtech.com) Received: from [10.177.171.220] (neutrino.centtech.com [10.177.171.220]) by mh1.centtech.com (8.13.1/8.13.1) with ESMTP id k8KDNv4P054078 for ; Wed, 20 Sep 2006 08:23:57 -0500 (CDT) (envelope-from anderson@centtech.com) Message-ID: <451140F8.9030500@centtech.com> Date: Wed, 20 Sep 2006 08:24:08 -0500 From: Eric Anderson User-Agent: Thunderbird 1.5.0.5 (X11/20060802) MIME-Version: 1.0 To: freebsd-hackers@freebsd.org References: <200609201250.k8KCo8sm048910@lurza.secnetix.de> In-Reply-To: <200609201250.k8KCo8sm048910@lurza.secnetix.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: ClamAV 0.87.1/1909/Tue Sep 19 21:58:44 2006 on mh1.centtech.com X-Virus-Status: Clean Subject: Re: numbers don't lie ... X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 20 Sep 2006 13:23:58 -0000 On 09/20/06 07:50, Oliver Fromme wrote: > Dmitry Morozovsky wrote: > > Oliver Fromme wrote: > > > Because buildworld is I/O-bound on systems with sufficiently > > > fast processors. > > > > > > Try putting the contents of /usr/src into a RAM disk and > > > repeat the benchmark. The numbers might look a little > > > different then. Of course, you should have sufficient RAM > > > in the machines -- If they're going to swap to the disks, > > > your benchmark won't be happy. > > > > > > I think putting /usr/obj onto a RAM disk is _not_ necessary > > > because of soft-updates, so the processes shouldn't block > > > on writes. > > > > My experiments show that if you have enough memory to host radmdrive for > > /usr/src you'd better leave it for caching - there were no statistically > > meaningful performance difference, at least on machines with 1G+ RAM. > > That might only be true if you have enough RAM to keep > _all_ buildworld files (src, obj, toolchain) in the cache > _and_ you pre-read all of /usr/src before actually starting > the buildworld, so it is in the cache. If you don't have > that much RAM, but enough to store /usr/src, then using > a RAM disk for it is a win. > > Reading /usr/src from a physical disk certainly requires > quite some I/O that takes more than zero time. But, in order to populate the ram disk, you must read /usr/src also from something, and that also takes time, which you should include in the full scope. Eric -- ------------------------------------------------------------------------ Eric Anderson Sr. Systems Administrator Centaur Technology Anything that works is better than anything that doesn't. ------------------------------------------------------------------------